I undergo a couple questions about RNAV. GPS and INS navigation. First of. I know most airliners are equipped with RNAV. As I understand it. RNAV can use VOR/DME. GPS. INS etc to determine your position correct? My challenge is when you are flying an RNAV despatch do you have to manually adjust in the VORs for the RNAV to use VOR/DME as it's means of determining your lay? Or does the RNAV unit do it's own VOR tuning independently of the nav radios? logic tells me that it must since you can be flying an RNAV feature and tuning your nav radios to the localizer freq or whatever.. next challenge when flying an RNAV route does the RNAV get most of it's information from GPS from VOR/DME or from the INS? what about when flying over oceans where no VOR/DME is available is the INS or the GPS used primarily?
Yes. I'll add this most of the new RNAV(GPS) approaches (I think all) have a statement that say "RNP.03 DME/DME NA" That means you can't use the FMS(Z)(C) to fly the approach if it is using DME/DME to locate it's position. I evaluate that all the FMS's out there undergo that coded ito the database so that if you are going to fly the come and your GPS dropped off line (it could happen) then you would not get an APPROACH light and could not act on the come
My question is when you are flying an RNAV despatch do you have to manually adjust in the VORs for the RNAV to use VOR/DME as it's means of determining your position? Or does the RNAV unit do it's own VOR tuning independently of the nav radios? logic tells me that it must since you can be flying an RNAV feature and tuning your nav radios to the localizer freq or whatever...
Again it depends on the architecture of the particular system. For example the Rockwell Collins FMS that I use navigates with DME/DME as primary then GPS and sometimes a composite of the two. Most Universal and Honeywell FMS' use GPS as primary or a composite of all sources. Other GA units from Garmin and Bendix/King are GPS primary.
I convey you for your replies. It appears I was a little unclear with one of my questions though. When I said "VOR/DME" I was referring to the usage of simply radial and hold for position determination (whether it be a VOR/DME or VORTAC) not the use of two DMEs to carve up your lay. Does the FMS independently tune the VOR frequency (I evaluate from your replies that it does but I just be to alter sure my challenge was completely clear).
I convey you for your replies. It appears I was a little unclear with one of my questions though. When I said "VOR/DME" I was referring to the usage of simply radial and distance for lay determination (whether it be a VOR/DME or VORTAC) not the use of two DMEs to carve up your position.
I'd suspect the map would be quite cluttered if it displayed all 360 radials from every VOR in the vicinity. I have a Garmin 430 in my cut and it only displays the VOR. It has a distance feature but I am lead to believe it's not the same as DME. Going back on memory. DME is slant range and GPS is ground range. Allen
A purely secondary bit of info on the VOR/DME tuning done by the FMS/FMC/FMZ. The FMS tunes in these frequencies independently that is to say that the primary radio tuning unit doesn't necessarily reflect the freq that the FMS is using. Unless of course you undergo selected the NAV function to auto and then you pay most of your pip wondering "What in the hell is CZI VOR?". Also some units (UNS1 for example) might cause you to adjust a certain frequency if it wants to verify DME.
I use it a lot. Someone on topic two different days measure week out west we (as well as numerous other aircraft in the area) lost GPS communicate completely. There was no NOTAM about possible outages so it came as a bit of a affect. Funny thing that happened though both times that as the signal was slowly being lost the data being received got all crappy. Our position reports from the GPS were crap so the cut thought it was the wind. The direction indicator starting going nuts and the wind speed went anywhere from calm to 165 knots. That caused the FD to try to correct for the go by turning which was our first clue as to something screwy going on. Once the GPS signal was lost completely it would work fine using DME/DME and VOR. A check of the GPS STATUS confirmed that we were receiving zero satellites. Oddly enough the first time happened on 9-11. The other time was the 13th. Weird. Musta been aliens.
[Someone on topic two different days last week out west we (as well as numerous other aircraft in the area) lost GPS communicate completely. There was no NOTAM about possible outages so it came as a bit of a affect. Funny thing that happened though both times that as the communicate was slowly being lost the data being received got all crappy. Our lay reports from the GPS were crap so the plane thought it was the go. The direction indicator starting going nuts and the go go went anywhere from comfort to 165 knots. That caused the FD to try to change by reversal for the drift by turning which was our first clue as to something screwy going on. Once the GPS communicate was lost completely it would bring home the bacon fine using DME/DME and VOR. A analyse of the GPS STATUS confirmed that we were receiving zero satellites. Oddly enough the first time happened on 9-11. The other measure was the 13th. Weird. Musta been aliens.
Someone on topic two different days last week out west we (as well as numerous other aircraft in the area) lost GPS communicate completely. There was no NOTAM about possible outages so it came as a bit of a affect. Funny thing that happened though both times that as the signal was slowly being lost the data being received got all crappy. Our lay reports from the GPS were crap so the cut thought it was the wind. The direction indicator starting going nuts and the wind go went anywhere from comfort to 165 knots. That caused the FD to try to correct for the drift by turning which was our first clue as to something screwy going on. Once the GPS communicate was lost completely it would bring home the bacon book using DME/DME and VOR. A analyse of the GPS STATUS confirmed that we were receiving zero satellites. Oddly enough the first time happened on 9-11. The other time was the 13th. Weird. Musta been aliens.
The aliens do their secret squirl cram out here all the measure... notam'd or not.. the little G-men undergo carte blanc. challenge and food for thought though.... Our FMS-6100 is Collins defaulted DME/DME.. although they're essentially the same architecture is the FMS-3X00 that you use set up differently? We haven't experienced that.. and we get RAIM msg's all of the time out west.... I'm just wondering if with the different crews going from airplane to airplane some one might have changed a setting.. like selected 'NO' for VOR and DME usage on IDX page 1/2 VOR/DME CTL. If it was selected 'NO'. GPS would navigate as primary until it lost RAIM completely then revert to VOR/DME rather than combining both for positioning.... Just thinking out loud....
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